Due to the way they are made, alkyl hydroperoxides are available only with a relatively high water content. Also, water is added as an especially cheap and suitable phlegmatizing agent for transportation and in storage, in order thus to assure safe handling of these hydroperoxide reagents which have a tendency to explosive degradation. For example, the technically very important tert.-butyl hydroperoxide (TBHP) is approved for transportation only as TBHP-70 (70% TBHP and 30% water) and as TBHP-80 (80% TBHP, approximately 8% di-tert.-butyl peroxide and 12% water). Although the water content of such reagents has no undesirable effect in a number of applications, as initiators in emulsion polymerization for example, it has been found, however, that any appreciable water content is undesirable in other organic syntheses, as for example in the case of asymmetrical epoxidation, and even prevents it in many cases. For a long time, therefore, efforts have been made to prepare concentrated, water-free solutions of alkyl hydroperoxides.
For example, P. D. Bartlett et al, in J. Am. Chem. Soc. 80, 1398 (1958), has proposed a method, which was later improved by Bock, Dissertation Univ. of Munich, 1968, to remove water from tert.-butyl hydroperoxide (TBHP) by means of an azeotropic vacuum distillation. In this process TBHP has to be warmed to about 50.degree. to 70.degree. C., which entails a high risk of explosion. Therefore this procedure is not appropriate for application on a technical scale.
In J. Org. Chem. 1983, 48, 3607-3608, J. G. Hill et all describe the use of benzene and toluene for the azeotropic removal of water: benzene or toluene is added to the aqueous TBHP solution and the water is distilled out with refluxing until a constant well temperature indicates the complete removal of the water. This process, however, likewise has the disadvantage that the temperature has to be raised to quite considerable temperatures, namely to as much as 107.degree. C. Consequently this method too is unsuitable for the industrial scale on account of thermal stress in a sealed distillation apparatus due to the problems that threaten safety. Moreover, the concentrations obtained by this method are too low.
H. Langhals et al., Chem. Ber. 113, 3662-3665 (1980), describes the use of molecular sieves for drying TBHP and expressly states that acid drying agents, such as concentrated sulfuric acid or phosphorus pentoxide are not suitable for removing water from TBHP containing water, since they are said to lead to the degradation of the peroxides. The process proposed by Langhals et al. for repeated drying with molecular sieves is very costly in time and material and therefore it is not suitable for production on a technical scale. Moreover, the molecular sieve used must be free of heavy metals and has to be given complicated treatment before use. Just for drying, the TBHP must, according to the; example given, be treated five times at -4.degree. C. for 3 hours to achieve sufficient water removal.
The invention therefore has the purpose of developing a simple drying process for tertiary alkyl hydroperoxides which can be performed on a technical scale with easily handled commercial chemicals.